Thanks to early detection through screening via a doctor, colon polyps may be found and removed before they develop into cancers — and colon cancers may be detected early, when the disease is easier to cure.

Colonoscopy can remove polyps as small as one millimetre or less. Once polyps are removed, they can be studied with the aid of a microscope to determine if they are precancerous or not.

Colonoscopy is similar to sigmoidoscopy—the difference being related to which parts of the colon each can examine. A colonoscopy allows an examination of the entire colon (1200–1500 mm in length). A sigmoidoscopy allows an examination of the distal portion (about 600 mm) of the colon, which may be sufficient because benefits to cancer survival of colonoscopy have been limited to the detection of lesions in the distal portion of the colon.

If you knew that the majority of deaths from colorectal cancer could be prevented if every adult 50 years or older got tested, would you do it? Unfortunately, that message falls on deaf ears for millions of us.

The pain associated with the procedure is not caused by the insertion of the scope but rather by the inflation of the colon in order to do the inspection. The scope itself is essentially a long, flexible tube about a centimetre in diameter, i.e. as big around as the little finger, which is less than the diameter of an average stool. The pain is said to be very uncomfortable and also burning.

The colon is wrinkled and corrugated, somewhat like an accordion or a clothes-dryer exhaust tube, which gives it the large surface area needed for digestion. In order to inspect this surface thoroughly the physician blows it up like a balloon, using an air compressor, in order to get the creases out. The stomach, intestines and colon have a so-called “second brain” wrapped around them, which autonomously runs the chemical factory of digestion.

It uses complex hormone signals and nerve signals to communicate with the brain and the rest of the body. Normally a colon’s job is to digest food and regulate the intestinal flora. The harmful bacteria in rancid food, for example, creates gas. The colon has distension sensors that can tell when there is unexpected gas pushing the colon walls out —thus the “second brain” tells the person that he or she is having intestinal difficulties by way of the sensation of nausea. Doctors typically recommend either total anaesthesia or a partial “twilight” sedative to either preclude or to lessen the patient’s awareness of pain or discomfort, or just the unusual sensations of the procedure. Once the colon has been inflated, the doctor inspects it with the scope as it is slowly pulled backwards. If any polyps are found they are then cut out for later biopsy.

Some doctors prefer to work with totally anesthetized patients inasmuch as the lack of any perceived pain or discomfort allows for a leisurely examination. Twilight sedation is, however, inherently safer than general anesthesia; it also allows the patients to follow simple commands and even to watch the procedure on a closed-circuit monitor. For these reasons it is generally best to request twilight sedation and ask the doctor to take his or her time despite any discomfort which the procedure may entail. Tens of millions of adults annually need to have colonoscopies, and yet many don’t because of concerns about the procedure.

Duodenography and colonography are performed like a standard abdominal examination using B-mode and color flow Doppler ultrasonography using a low frequency transducer — for example a 2.5 MHz — and a high frequency transducer, for example a 7.5 MHz probe. Detailed examination of duodenal walls and folds, colonic walls and haustra was performed using a 7.5 MHz probe. Deeply located abdominal structures were examined using 2.5 MHz probe. All ultrasound examinations are performed after overnight fasting (for at least 16 hours) using standard scanning procedure. Subjects are examined with and without water contrast. Water contrast imaging is performed by having adult subjects take at least one liter of water prior to examination. Patients are examined in the supine, left posterior oblique, and left lateral decubitus positions using the intercostal and subcostal approaches. The liver, gall bladder, spleen, pancreas, duodenum, colon, and kidneys are routinely evaluated in all patients. With patient lying supine, the examination of the duodenum with high frequency ultrasound duodenography is performed with 7.5 MHz probe placed in the right upper abdomen, and central epigastric successively; for high frequency ultrasound colonography, the ascending colon, is examined with starting point usually midway of an imaginary line running from the iliac crest to the umbilicus and proceeding cephalid through the right mid abdomen; for the descending colon, the examination begins from the left upper abdomen proceeding caudally and traversing the left mid abdomen and left lower abdomen, terminating at the sigmoid colon in the lower pelvic region. Color flow Doppler sonography is used to examine the localization of lesions in relation to vessels. All measurements of diameter and wall thickness are performed with built-in software. Measurements are taken between peristaltic waves.